1. Field of the Invention
This invention relates to crossflow water cooling towers and especially improved drift eliminator construction for effectively removing entrained water particles from generally horizontally directed air currents leaving the tower fill structure. More particularly, it is concerned with such a drift eliminator which serves to remove a significant portion of the entrained water particles in the air leaving the tower fill, while at the same time avoiding undue pressure drops; in addition, the construction of the eliminator allows individual water drainage from the respective diversion paths, so that troublesome water blockage and possible re-entrainment typically associated with crossflow eliminator structure is avoided.
2. Description of the Prior Art
In evaporative water cooling towers of the crossflow variety, thermal energy is removed from initially hot water by causing the latter to gravitate through a surface-increasing fill assembly in crossflowing intersecting relationship to currents of cool air directed through the fill. Drift eliminators are usually provided to remove entrained droplets or particles from the air leaving the tower fill structure. If drift eliminator structures are not employed in such towers, substantial quantities of water can be discharged into the atmosphere. This results in undesirable operating conditions leading to excessive wetting of surrounding areas and corresponding coating thereof with mineral deposits. In addition, icing of adjacent equipment and structures can readily occur during wintertime operations. Thus, adequate drift elimination is very necessary with evaporative type cooling towers, especially when large towers are used in metropolitan areas, as part of a large industrial complex where cold weather occurs, or because of ecological concerns where saline water is circulated through the tower.
Although it is desirable from a theoretical standpoint to remove essentially all water particles from cooling tower discharge air, as a practical matter this is an impossibility. Given this constraint, it is important that the particle size distribution of discharged water droplets be the most desirable from the standpoint of avoiding excessive wetting closely adjacent the tower. If, for example, the entrained water particles are relatively large and hence massive, they will tend to deposit on equipment or structures close to the tower. On the other hand, if the entrained particles are of relatively small size, there is a greater tendency for the water to spread and diffuse over a much larger area. In the latter case, undue icing or damage to adjacent equipment or the like is avoided. Therefore, it is important not only to remove as much water as possible on an absolute basis from fill-derived air, but also to ensure that the water which does escape to the atmosphere be predominantly of small particle size.
U.S. Pat. No. 4,040,824 describes a dual path drift eliminator structure which is particularly designed for crossflow cooling towers. The drift eliminator described in U.S. Pat. No. 4,040,824 includes side-by-side cellular drift eliminator sections separated by an elongated, upright, channel or spacing which permits water to drain vertically from the eliminator.
U.S. Pat. No. 4,333,749 describes a triple path drift eliminator structure which is particularly designed for counterflow water cooling towers. The use of a three-path drift eliminator in counterflow water cooling towers has resulted in greatly enhanced drift elimination while avoiding undue pressure drops.
While the dual path drift eliminator structure described in U.S. Pat. No. 4,040,824 and the three path counterflow drift eliminator structure described in U.S. Pat. No. 4,333,749 both represent real advances in the art for crossflow and counterflow drift eliminator structures respectively, there has heretofore been no attempt to provide a three-path drift eliminator structure for crossflow cooling towers. This is partially due to the unresolved problem of water blockage in crossflow eliminator structures of extended axial length, as is needed to accommodate three path eliminator structures. Accordingly, there is a need for an improved cellular-type drift eliminator structure which provides the enhanced drift elimination capabilities of a three-path eliminator structure for crossflow water cooling towers, which provides for downward water drainage, without imposing undue pressure drops by the use thereof.